Many thin film PV device and, particularly, NDSC devices, as of the type disclosed in the above patents, are capable of being fabricated in a laminate arrangement between two large area substrates without undue expense. One typical arrangement involves two glass substrates, each utilising an electrically conducting coating upon the internal surface of the substrate. Another typical arrangement involves the first substrate being glass or polymeric and utilising an electrically conducting coating upon the internal surface of the substrate, with the second substrate being polymeric or metallic. In some arrangements, the internal surface of said second polymeric substrate is coated with an electrically conducting coating, whereas in other arrangements, said second polymeric substrate comprises a polymeric foil laminate, utilising adjacent electrically conductive material, such as carbon. Also, in some arrangements, the external surface may be a laminated metal film, and in other arrangements, the external surface may be coated by a metal. In other arrangements the substrate is made of metal or metallic mesh or the internal surface of the substrate is coated by metal. At least one of said first and second substrates is substantially transparent to visible light, as is the attached transparent electrically conducting (TEC) coating.
In general, a photovoltaic device comprises active photovoltaic regions, connecting means to connect these regions electrically and dividing means to separate these regions.
In particular, the active photovoltaic regions of NDSC device comprise a working electrode of nanoparticulate dye-sensitised wide band gap semiconductor (e.g. titanium dioxide known as titania) attached to one conductive coating; a counter electrode, typically consisting of a catalytic layer attached to the other conductive coating or to a conductive material; and an electrolyte containing a redox mediator placed between the working and the counter electrodes.
Many NDSC module designs would be advantaged by an increased size of individual NDSC devices. However, such transparent electrical conductors (TEC), which usually comprise a metal oxide(s) or metallic mesh, have relatively high resistivity when compared with normal metal conductors, resulting in higher than sought resistive losses for large area NDSC device, which affects the efficiency of the NDSC device especially in high illumination conditions.
In one arrangement, described in the prior art, these losses are reduced by the use of connecting means such as a pattern of electrically conductive material (ECM) in the form of bus bars, pads, grid of lines or any other pattern on the TEC coating(s) or inlaid or surface laid conductive mesh or wires. The said electrically conducting means occupy certain part of surface of a photovoltaic module, thus reducing area available for the active photovoltaic regions of NDSC. This results in reduction of overall efficiency of NDSC device since only a part of solar radiation incident to the device strikes its active photovoltaic regions.
In another arrangement, described in the prior art, these losses are reduced by forming two or more relatively small separate NDSC devices and separating and connecting them internally within a single NDSC module. Once again, the internal connectors and/or separators between the separate NDSC devices occupy certain part of surface of the photovoltaic module, thus reducing overall efficiency of NDSC device.